PSA stands for prostate-specific antigen. It is a protein found in prostate cells. It can be detected at a low level in the blood of all adult men.

This article discusses the blood test to measure the amount of PSA in a man's blood.

Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

No special preparation is usually needed.

When the needle is inserted to draw blood, some people feel moderate pain while others feel only a prick or stinging sensation. Afterward, there may be some throbbing or a bruise.

This test is done to screen for prostate cancer. It is also used to monitor patients after prostate cancer treatment.

Several conditions besides cancer can cause the PSA level to rise, including:

• Benign prostatic hyperplasia
• Prostatitis
• Urinary tract infections

Discuss with your doctor or health care provider whether a PSA test is appropriate for you.

Normal values vary with age. Older men typically have slightly higher PSA measurements than younger men. Men with a larger prostate will also have higher PSA values.

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

A high PSA level has been linked to an increased chance of having prostate cancer. However, a high PSA level does not mean that you definitely have prostate cancer. A high PSA level only identifies patients at higher risk of having prostate cancer. People at higher risk may need to have more tests.

A PSA of 4 nanograms per milliliter (ng/mL) is abnormally high for most men and may indicate the need for a prostate biopsy.

Keep in mind that although PSA testing is an important tool for detecting prostate cancer, it is not foolproof.

Greater-than-normal PSA levels may indicate:

• Benign prostatic hypertrophy
• Prostate cancer
• Prostatitis
• Prostate infection
• Urinary tract infection
• Recent urinary catheterization
• Recent urinary tract operation

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

Discuss the benefits and risks of testing with your doctor to determine whether screening is right for you.

• Potential benefits include early diagnosis of cancer
• Potential risks include increased health care costs, unnecessary invasive testing (biopsy) and treatment

The American Urologic Association, American Cancer Society, and National Comprehensive Cancer Network recommend that:

• All men ages 50 - 75 have annual PSA tests
• You get tested at an earlier age (age 40 or 45) if you are of African-American heritage or have a father or brother with prostate cancer

However, these guidelines are not recommended for everyone. Many health organizations, including the US Preventive Services Task Force, do not recommend routine PSA testing.

Lin K, Lipsitz R, Miller T, Janakiraman S. U.S. Preventive Services Task Force. Benefits and harms of prostate-specific antigen screening for prostate cancer: an evidence update for the U.S. Preventive Services Task Force. Ann Intern Med. 2008;149:192-199.

Lim LS, Sherin K; ACPM Prevention Practice Committee. Screening for prostate cancer in U.S. men ACPM position statement on preventive practice. Am J Prev Med. 2008;34:164-170.

Walsh PC, DeWeese TL, Eisenberger MA. Clinical practice. Localized prostate cancer. N Engl J Med. 2007;357:2696-2705.

Walter LC, Bertenthal D, Lindquist K, Konety BR. PSA screening among elderly men with limited life expectancies. JAMA. 2006;296:2336-2342.